//C11:ep11_7_2.c: three students scores,used dynamic linklist.
// print node.
void print(struct student_st *head)
{
    struct student_st *p;
    printf("\nNow , these %d  records are:\n",n);
    p = head;
    if(head != NULL)
    {
        do{
            printf("%ld %5.2f\n", p->num, p->score);
            p = p->next;
        }while(p != NULL);
    }
}